A wireless local area network (WLAN) is a flexible data communications system that can either replace or extend a wired LAN to provide additional functionality. Using radio frequency (RF) technology, WLANs transmit and receive data over the air, through walls, ceilings and even cement structures without wired cabling. A WLAN provides all the features and benefits of traditional LAN technology, such as Ethernet and token ring, but without the limitation of being tethered together by a cable. This provides greater freedom and increased flexibility.
A WLAN is a network in which a mobile user can connect to a LAN through a RF connection. The Institute of Electrical and Electronic Engineers (IEEE) 802.11 Standard (e.g., IEEE Std. 802.11-1997, 802.11a, 802.11.e, 802.11n, etc.) specify technologies for WLANs. There are several technologies for WLANs including 802.11 Standard, Hyper LAN 2 and future potential standards for any point-to-point wireless link or network. Accordingly, high bandwidth allocation for WLANs provides a solution for implementing a network within structures at a relatively low cost without having to wire such structures to implement the network.
Wireless devices that operate according to an IEEE 802.11 Standard include two main parts: 1) a physical layer (PHY) signaling control device; and 2) a medium access control (MAC) device. The function of the PHY device is to transfer data packets over an RF interface. Among other things, the function of the MAC is to fairly control access to the shared RF interface.
The minimal MAC protocol consists of two frames, (1) a frame sent from a transmitter to a receiver; and (2) an acknowledge (ACK) from the receiver that the frame was received correctly, referred to herein as a “single packet transmission mode.” If a transmitter has multiple packets to send to the receiver, some versions of the 802.11 standard require the transmitter to wait for an ACK after the transmission of each packet. In addition, the transmitter must wait for a particular time interval, referred to as the “inter-frame space” (IFS), after receiving the ACK and before transmitting the next packet.
The 802.11 Task Group N (TGn) was designed with the goal of increasing the peak throughput of 802.11 WLANs. TGn's goal is to achieve 100 megabits per second (MBPS) network throughput. One of the modifications for achievement of increasing of the throughput of 802.11 WLAN networks is the use of multiple input, multiple output (MIMO) operations. In accordance with MIMO, the number of transmission and receive antennas used by an 802.11 transceiver may include multiple transmission antennas and multiple receive antennas.